/Engine/Source/Runtime/Core/Public/Math/Rotator.h
Checks whether rotator is nearly zero within specified tolerance, when treated as an orientation. This means that TRotator(0, 0, 360) is "zero", because it is the same final orientation as the zero rotator.
true if rotator is nearly zero, within specified tolerance, otherwise false.
bool IsNearlyZero ( T Tolerance ) const